The present invention is directed to airfoil components for gas turbine engines and, more particularly, to contouring of the airfoil.
Gas turbine engines operate by passing a volume of high-energy gases through a plurality of stages of vanes and blades in order to drive turbines to produce rotational shaft power. The shaft power drives a compressor to provide compressed air to a combustion process that generates the high-energy gases. Additionally, the shaft power may be used to drive a generator for producing electricity or to drive a fan for generating thrust. In order to produce gases having sufficient energy to drive the compressor and generator/fan, it is necessary to compress the air to elevated pressures and temperatures, and combust the air at even higher temperatures.
The vanes and blades each include an airfoil that extends through a flow path in which the high-energy gas moves. The turbine blade airfoils are typically connected at their inner diameter root sections to a rotor, which is connected to a shaft that rotates within the engine as the blades interact with the gas flow. The rotor typically comprises a disk having a plurality of axial retention slots that receive mating root portions of the blades to prevent radial dislodgment. Blades typically also include integral inner diameter platforms that prevent the high temperature gases from penetrating through to the retention slots. The turbine vane airfoils are typically suspended from an outer engine case at an outer shroud structure and include an inner shroud structure that aligns with the blade platforms.
The flow of the hot gas around each airfoil produces localized potential fields that interact with adjacent airfoil rows. For example, the rotating blade airfoils pass through and impact the static pressure field developed by the suction side of the upstream vane airfoils. These interactions adversely impact the effectiveness of each airfoil, thereby reducing the overall engine efficiency. Various approaches have been developed for addressing these suction side potential fields. For example, U.S. Pat. No. 6,358,012 to Staubach discusses providing a concave suction side contour between convex suction side contours at the throat of adjacent airfoils to reduce shock effects in supersonic blade applications. Also, U.S. Pat. No. 5,228,833 to Schönenberger et al. discusses placing a concave portion along the suction side extending a distance forward from the trailing edge equal to the throat length in order to mitigate losses associated with the deceleration of airflow along the suction side under subsonic conditions. U.S. Pat. No. 5,292,230 to Brown discloses placing a straight portion along the suction side from the trailing edge to a gauging point in a steam turbine vane airfoil. There is, however, a continuing need to improve the efficiency of airfoils, particularly with respect to reducing potential field interactions and increasing overall engine efficiency.